Melt spinning apparatus



y 1955 H. WEBER EI'AL 2,707,306

MELT SPINNING APPARATUS Filed Aug. 22, 1952 i i 72 a 77 8/ i 4 73 j 79 "H ll I ll :':::i

13min .INVENTORS.

HAROLD WEBER 76 ROBERT H.ROUGHSEDGE ATTORNEYS.

United States Patent MELT SPINNING APPARATUS Harold Weber, Bloomfield, and Robert H. Roughsedge, Ramsey, N. J., assignors to Celanese Corporation of America, New York, N. Y., a corporation of Delaware Application August 22, 1952, Serial No. 305,746

6 Claims. (Cl. 18-8) This invention relates to spinning and relates more particularly to an improved process and apparatus for the production of filamentary materials by the melt-spinning of a filament-forming material.

In the production of filamentary materials, particularly multi-filament filamentary materials such as yarn and the like, by the melt-spinning process, a filament-forming material is raised to a temperature above its melting point and the molten material is then pumped through a spinnerette containing a plurality of spinning apertures therein. The filamentary materials emerge from the spinnerette into a cooling medium, such as air, wherein they are cooled rapidly to a temperature below the melting point of the filament-forming material thereby causing the filamentary materials to set. The uniformity of the filamentary materials depends upon three factors; the uniformity in the volume rate at which the filamentforming material is forced through the apertures in the spinnerette, the uniformity in the density of the filamentforming material and the uniformity of the heating of the filament-forming material. Through the use of suitably designed pumping means, the volume rate at which the filament-forming material is forced through the apertures in the, spinnerette may beheld substantially constant Within extremely narrow limits. To bring the filamentforming material to a uniform density, however, presents a number of problems. Voids in the filament-forming material must be eliminated therefrom. In addition, gases and water vapor must be removed from the filamentforming material since their presence would cause an effective change in the uniformity of the filamentary materials being produced. The low heat conductivity of the filament-forming material makes it difficult to heat the said material to a uniform temperature. a H According to prior melt-spinning processes, the filament-forming material is brought to a molten state and is then cooled until it solidifies, either during its production or at some other point in its processing prior to the spinning operation itself. As a result, the filament-forming material employed for spinning is relatively dense and free from voids. In addition, it is the practice during the spinning operation to establish a relatively large pool of molten filament-forming material and to draw the filament-forming material from said pool as required during spinning. The filament-forming material tends to reach a substantially uniform density during the period of time it remains in the molten state in said pool. It is possible through the use of one or both of the foregoing expedients to obtain filamentary materials of a high degree of uniformity. There is, however, a considerable tendency for the filament-forming material to decompose or degrade both during the preliminary melting of the said material and during the relatively long period of time it remains in a molten state during the spinning operation. .This tendency to decompose or degrade is particularly marked with certain types of filament-formingjmaterial causing a serious loss of desirable properties in the final. products. Despite the long. period of time for whichthe filament- 2,707,305 Patented May 3, 1955 forming material is in the molten state, it does not always reach a uniform temperature. Moreover, when the filament-forming materials are not normally brought to a molten state during their production, but are obtained in a relatively bulky form containing a large number of voids and of low density, the necessity for carrying out the preliminary melting not only tends to cause the filamentforming material to decompose or degrade, but also adds to the complexity and expense of the entire process.

It is an important object of this invention to provide a process and apparatus for the production of filamentary materials by the melt-spinning of a filament-forming material which will be free from the foregoing and other difliculties and which will be especially efificient in operation and simple in construction.

A further object of this invention is to provide a process and apparatus for the production of filamentary materials by the melt-spinning of a filament-forming material wherein the filament-forming material is melted and brought to a uniform density and temperature and is forced through the apertures in a spinnerette in one continuous operation.

Other objects of this invention, together with certain details of construction and combinations of parts, will be apparent from the following detailed description and claims.

According to the present invention there is provided an apparatus comprising a chamber having means for the introduction of a filament-forming material. The chamber is also provided with means for applying a vacuum thereto whereby gases and water vapor may be removed from the filament-forming material. To assist in theremoval of gases and water vapor from the filament-forming material, it is desirable to heat the chamber to a temperature above that at which water boils under the particular degree of vacuum applied, but below that at which the filament-forming material melts. For example, when a vacuum of 28 inches of mercury is applied to the chamber, the temperature of said chamber may be maintained at between about 65 and C. Positioned within the chamber is a feed screw which moves the filamentforming material, which is in an unmolten state, from the chamber into a heated jacket which is fitted closely to the feed screw and in which the filament-forming material is melted. The feed screw is designed so that it will tend to feed a substantially larger volume of filamentforming material into the entrance to said jacket than out of the discharge from said jacket. As a result, considerable pressure will be applied to the filament-forming material thereby tending to remove all voids therefrom and bringing the same to a substantially uniform density. The ratio of feeds by volume to the inlet to and from the discharge from said jacket should be at least equal to the inverse ratio of the specific gravities of the filament-forming material at the point where it enters the jacket in an unmolten state to that at the point where it leaves the jacket in the molten state. Advantageously the ratioof feeds is at least about 5% in excess of this value or between about 5 and 25% in excess of this value to compensate for any irregularities in the specific gravity of the unmolten filament-forming material. Higher ratios may also be employed if provision is made to permit slippage of the material between the screw and the jacket to avoid the development of excessive pressures. A particularly desirable way of achieving this ratio of feeds is to taper the flight of the feed screw toward its discharge end while leaving the root diameter of the feed screw unchanged. With this construction it is also possible to reduce the thickness of the filament-forming material to an extremely low value, say less than about 0.03 inches; so that all of said filament-forming material will be brought to a uniform temperature. Upon leaving the jacket, the molten filament-forming material may be passed directly, or through a filter pack, to a spinncrette having a plurality of spinning apertures therein from which it will emerge in the form of a yarn. It may, however, be desirable to pass the molten filament-forming material leaving the jacket to a gear pump which will meter the said material directly, or through a filter pack, to the spinnerette.

The process and apparatus of this invention are particularly well suited for the production of multi-filament filamentary materials in which the individual filaments have a low denier, i. e., a denier of less than about or preferably less than about 5. At these low deniers, any irregularities in the feed or density of the filamentary material will result in large percentage changes in the denier of the filaments, leading to the production of products that are not commercially acceptable. Even when starting with filament-forming materials that are bulky and of non-uniform density and contain gases and water vapor it has been found possible through the use of this invention to obtain products that have a substantially uniform denier.

Filament-forming materials that may be employed in carrying out this invention include, for example, polyamides, polyurethanes, polytriazoles, polyesters and the like.

A preferred embodiment of this invention is shown in the accompanying drawing wherein Fig. 1 is a side-elevational view, partly in section, of the apparatus, and

Fig. 2 is a cross-sectional view, taken on the line 2-2 in Fig. 1, in the direction of the arrows.

Referring now to the drawing, the reference numeral 11 designates a conduit through which a filament-forming material, which may be in the form of chips, flakes, powder or the like, is fed to a feed valve, indicated generally by reference numeral 12. The feed valve 12 comprises a cylindrical casing 13 in which is rotatably positioned a pair of intersecting plates 14 that divide the casing into quadrants 15. The pair of plates 14 is rotated continuously or intermittently during operation by any'suitable means (not shown). The upper quadrant 15 is filled with filament-forming material from the conduit 11. As the pair of plates 14 rotates, this quadrant will be moved to the lowermost position so that the filamentfo'rming material will be discharged from said quadrant into a conduit 16 which leads the filament-forming material to the main portion of the spinning apparatus, indicated generally by reference numeral 17. The conduit 16 is provided with a cut-off valve 18 whereby the feed 'of filament-forming material to the spinning apparatus 17 may be interrupted at any time.

a The spinning apparatus17 comprises a tubular member 19 having flanges 21 and 22 secured to its upper and lower ends, respectively. A tubular fitting 23 having a flange 24 extending around its periphery projects into the upper end of the tubular member 19 and is secured in place by means of bolts 25 that extend through the flanges 21 and 24. The tubular fitting 23 carries a plurality of anti-friction bearings 26 in which is rotatably mounted the shank 27 of a 'feed screw, indicated generally by reference numeral 28. The shank 27 of the feed screw 28 is fastened by means of a pin 29 to a stub shaft 31 which is keyed by means of a key 32 to a drive coupling 33 driven by a suitable means (not shown) to rotate the feed screw 28.

I Positioned internally of the tubular member 19 below the tubular fitting 23 is a second tubular member 34. A tubular sleeve 35, secured to a disc 36 fastened to the feed screw 28 for rotation therewith, rides internally of the tubular member 34, being lapped or otherwise closely seated in said tubular member so as to produce an air tight seal with said member. The tubular member '34 which is stationary, is provided with'an opening 37 in its side to whichthe filament-forming material is directed'by the conduit 16. Av similar opening'38 is provided in the side of the tubular sleeve 35 so that when the rotation of the sleeve 35 brings the openings 37 and 38 into alignment, a charge of filament-forming material will enter chamber 39 formed by the said sleeve. When the openings 37 and 38 are not in alignment, the chamber 39 will be sealed from the atmosphere.

Means are provided to evacuate the chamber 39 so as to remove gases and water vapor from the filament-forming material. This means comprises a vacuum conduit 41 which is connected to the chamber 39 by means of apertures 42 and 43 in the walls of the tubular members 19 and 34, respectively, and apertures 44 in the disc 36. To keep from drawing filament-forming materials into the vacuum system and from imposing an excessive burden on the vacuum system when the openings 37 and 38 come into alignment, a block 45 is fastened by means of a set screw 46 to the feed screw 28. The block 45 is generally of smaller diameter than the internal diameter of the tubular member 37 around the major portion of its periphery, but bears against the tubular member 34 at a point diametrically opposed to the position of the opening 38. The block 45 is lapped or otherwise closely fitted against the tubular member 34 so as to form an air tight seal therewith. As a result, when the rotation of the feed screw 28 carries the openings 37 and 38 into alignment, the block 45 will close the aperture 43 so as to seal off the vacuum line 41 from the chamber 39. Then, when the continued rotation of the feed screw 28 carries the openings 37 and 38 out of alignment, the block 45 will move away from the aperture 43 so as' again to apply a vacuum'on the chamber 39. A screen 47 interposed between the chamber 39 and the conduit 41 further insures against any particles of filament-forming material being drawn into the vacuum system.

The filament-forming material that is introduced into the chamber 39 is moved through said chamber by the flight 48 with which the lower portion of the feed screw 28 is provided. The flight 48 moves the filament-forming material through a conical adapter 49 into a jacket 51 which is fitted closely to the said flight. The jacket 51 and the flight '48 are both tapered. Because of this taper, the flight 48 will tend to feed a larger quantity by volume of filament-forming material into the entrance to the jacket 51 than through the remainder of said jacket. This will build up a pressure on the filament-forming material thereby tending to eliminate all voids therefrom. The taper of the jacket 51 and the flight 48 also permit the clearance between said members to be controlled closely in a simple manner'by inserting a shim 52 of suitable thickness between the flanges 21 and 24 to shift the feed screw 28 axially of the jacket 51. For example, if the taper of the flight 48 and the jacket 51 is $6 and said members are in contact, a clearance of 0.0001 inch can be produced between said members by inserting a 0.005 inch shim 52 between the flanges 2'1 and '24 to 'shiftthe feed screw by this amount. Tapers up to :about A permit such close clearances between the flight48 and the jacket 51 to be readily achieved. Because it is possible to obtain such close clearances between the flight 48 and the jacket 51, a very efficient workingof the filament-forming material can be readily achieved. The taper of the flight 48 and the jacket 51 also permit a reduction in the thickness of the molten material to insure a uniform working thereof.

The first portion of the jacket 51 through which the filament-forming material moves is heated by means of a fluid that flows through a feed pipe 53 into a chamber 54 that encircles the jacket 51'and'then outof said chamber through a discharge pipe 55. The chamber 54 is provided with upper and lower flanges 56 and 57 and is held in place by means of bolts 58 that extend through the flanges 22 and 56. A thermal insulating gasket 59 is interposed between the flanges 22 and 56 to minimize the transfer of "heat therebetween and to assure better thermal control The first portion'o'f" the jacket 51 is heated to ate'mpera'ture suchas to (a) prevent melting of the filament-forming material, since if such melting occurred the filament-forming material would tend to form a bridge at this point or in the conical adapter 49 and thereby interrupt continued feed of said material, and (b) boil ofi? water and raise the temperature enough to remove primary gases without decomposing the material. The next portion of the jacket 51 is heated by means of a fluid that flows through a feed pipe 61 into a chamber 62 encircling said jacket and then out of said chamber through a discharge pipe 63. The final portion of the jacket 51 is heated by means of a fluid that flows through a feed pipe 64 into a chamber 65 and then out of said chamber through a discharge pipe 66. The chambers 62 and 65 are formed as a unit and are provided with an upper flange 67 which is secured to the flange 57 by means of bolts 68. A thermal insulating gasket 69 is interposed between the. flanges 57 and 67 to minimize the transfer of heat therebetween. Depending upon the properties of the filament-forming material, it may be desired to supply fluids having the same temperature to the chambers 62 and 65. In some cases, itmay be desirable to supply a fluid having a higher temperature to the chamber 62 so as to melt the filament-forming material quickly and then bring it to the proper spinning temperature. In still other cases, the fluid supplied to the chamber 62 may be at a lower temperature so as to begin the melting of the filament-forming material slowly.

Upon emerging from the jacket 51, the molten filamentforming material, which now has a substantially uniform density, passes through a screen 71 to a gear pump 72. The molten filament-forming material then flows through a filter pack 73 to a spinnerette 74 having a plurality of apertures 75 therein from which. it emerges as filaments 76. To maintain the filament-forming material at the proper spinning temperature, the gear pump 72, the filter pack 73 and the spinnerette 74 are enclosed in a chamber 77 into which a heating fluid is introduced through a feed pipe 78 and from which it is discharged through a discharge pipe 79. Channelling of the fluid as it flows through the chamber 77 is prevented by means of a spiral wrap of wire 81 which almost fills the space between the walls of said chamber.

Example Particles of 4,4-polyurethane obtained by the reaction of 1,4-tetramethylene diamine with the bis-chloroformate of 1,4-butanediol, which particles have never been melted and are bulky and filled with voids, are ground to a powder which will pass an 8 mesh screen. The powder is melt spun in the apparatus shown in the accompanying drawing. There are obtained filamentary materials of substantially uniform denier and good physical properties.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention what we desire to secure by Letters Patent is:

1. An apparatus for the production of filamentary materials by the melt-spinning of a filament-forming material, comprising a chamber, means for intermittently entering a filament-forming material into said chamber, means for applying a vacuum to said chamber to remove gases and water vapor from the filament-forming material, means for automatically disconnecting the vacuum applying means from said chamber during the entrance of the filament-forming material into said chamber, a heated jacket, a feed screw for feeding the filament-forming material from said chamber to and through said jacket, whereby the filament-forming material is caused by melt and pressure is applied to the molten material to free said molten material of voids and to bring the same to substantially uniform density and a spinnerette for converting the molten filament-forming material into filamentary material.

2. An apparatus for the production of filamentary materials by the melt-spinning of a filament-forming material, comprising a chamber, means for intermittently entering a filament-forming material into said chamber, means for applying a vacuum to said chamber to remove gases and water vapor from the filament-forming material, means for automatically disconnecting the vacuum applying means from said chamber during the entrance of the filament-forming material into said chamber, a jacket, means for differentially heating said jacket whereby that part of said jacket near the entrance thereto is heated to a temperature below the melting point of the filament-forming material to prevent premature melting of said material and the remainder of said jacket is heated above the melting point of the filament-forming material, a feed screw, having the same taper as said jacket and being axially shiftable with respect to said jacket to adjust the amount of clearance therebetween, for feeding the filament-forming material from said chamber to and through said jacket, whereby the molten material is freed of voids and brought to a substantially uniform density, and a spinnerette for converting the molten filamentforming material into filamentary material.

3. An apparatus for the production of filamentary materials by the melt-spinning of a filament-forming material, comprising a chamber, means for intermittently entering a filament-forming material into said chamber,

means for applying a vacuum to said chamber to re move gases and water vapor from the filament-forming material, means for automatically disconnecting the vacuum applying means from said chamber during the entrance of the filament-forming material into said chamber, a jacket, means for differentially heating said jacket whereby that part of said jacket near the entrance thereto is heated to a temperature below the melting point of the filament-forming material to prevent premature melting of said material and the remainder of said jacket is heated above the melting point of the filament-forming material, a feed screw, having the same taper as said jacket and being axially shiftable with respect to said jacket to adjust the amount of clearance therebetween, for feeding the filament-forming material from said chamber, to and through said jacket, whereby the molten material is freed of voids and brought to a substantially uniform density, a gear pump for metering the molten filament-forming material, and a spinnerette for converting the molten filament-forming material from the gear pump into filamentary material.

4. An apparatus for the production of filamentary materials by the melt-spinning of a filament-forming material, comprising a tubular member, a second tubular member positioned internally of said first tubular member, a tubular sleeve positioned internally of said second tubular member and forming a chamber for re ceiving the filament-forming material, means for applying a vacuum to said chamber to remove gases and water vapor from the filament-forming material, a jacket, 2. feed screw for feeding the filament-forming material from said chamber to and through said jacket, openings in the walls of said second tubular member and said tubular sleeve, means connecting said tubular sleeve to said feed screw whereby the rotation of the feed screw will bring said openings into alignment intermittently for permitting the filament-forming material to enter said chamber, means for heating the jacket to melt the filament-forming material, and a spinnerette for converting the molten filament-forming material into filamentary material.

5. An apparatus for the production of filamentary materials by the melt-spinning of a filament-forming material, comprising a tubular member, a second tubular member positioned internally of said first tubular member, a tubular sleeve positioned internally of said second tubular member and. forming a chamber for receiving the filament-forming material, means for. applying a vacuum to. said. chamber to remove gases. and. water vapor from the. filament-forming material, a jacket, a feed. screw for feeding the filament-forming material. from said. chamber totand through said jacket, said jacket and said feed screw being tapered whereby said feed screw has. a higher rate offeed at the inlet to said jacket than. at the outlet from. said jacket to. place the filamentf'orming material under pressure and eliminate voids therefrom, means for shifting the feed. screw axially with respect to the jacket to adjust the clearance between the jacket and the feed screw, openings in. the walls of said second tubular member and said tubular sleeve, means connecting said tubular sleeve to said. feed screw where.- by the rotation of the feed" screw will' bring, said openings into alignment intermittently for permitting the filamentforming material to enter said chamber, means for heating the jacket. to melt the filament-formingmaterial, and

a spinnerette for converting the molten filamenbforming said chamber to and through said jacket, said jacket and said feedscrew being tapered whereby said: feed screw has a higher rateof feed at the inlet to said' jacket than at the outlet from said jacket to place the filament-formingmaterial under pressure and eliminate voids there- 110,111,. means. for shifting; the feed. screw axially with respect to the. jacket to. adjust the: clearance between, the jacket. and the. feed screw, openings in the walls of said second tubular member and said tubular sleeve, means.

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1. AN APPARATUS FO THE PRODUCTION OF FILAMENTARY MATERIALS BY THE MELT-SPINNING OF A FILAMENT-FORMING MATERIAL, COMPRISING A CHAMBER, MEANS FOR INTERMITTENTLY ENTERING A FILAMENT-FORMING MATERIAL INTO SAID CHAMBER MEANS FOR APPLYING A VACUUM TO SAID CHAMBER TO REMOVE GASES AND WATER VAPOR FROM THE FILAMENT-FORMING MATERIAL, MEANS FOR AUTOMATICALLY DISCONNECTING THE VACUUM APPLYING MEANS FROM SAID CHAMBER DURING THE ENTRANCE OF THE FILAMENT-FORMING MATERIAL INTO SAID CHAMBER, A HEATED JEACKET, A FEED SCREW FOR FEEDING THE FILAMENT-FORMING MATERIAL FROM SAID CHAMBER TO AND THROUGH SAID JACKET, WHEREBY THE FILAMENT-FORMING MATERIAL IS CAUSED BY MELT AND PRESSURE IS APPLIED TO THE MOLTEN MATERIAL TO FREE SAID MOLTEN MATERIAL OF VOIDS AND TO BRING THE SAME TO SUBSTANTIALLY UNIFORM DENSITY AND A SPINNERETTE FOR CONVERTING THE MOLTEN FILAMENT-FORMING MATERIAL INTO FILMENTARY MATERIAL. 